1. Field of the Invention
The present invention relates to a fine adjusting mechanism for a cutting tool, and more particularly to a fine adjusting mechanism for a boring cutter for proceeding with fine adjustment of the diameter of the bore to be formed and for compensating wear in the boring cutter.
2. Description of the Related Art
FIG. 19 of the drawings illustrates a conventional cutting tool having a cutter shaft 10 with an inclined through-hole (not labeled) and a cutter 11 extended through the inclined through-hole and secured in place by screws 12. The cutter shaft 10 is rotated by a main shaft (not shown) of a processing machine (not shown), thereby forming a bore upon rotation of the cutter 11. When adjustment in the diameter of the bore to be formed is required, the screws 12 are loosened, and the cutter shaft 10 is rotated by the main shaft, such that a radius R (FIG. 20) from the tip of the cutter 11 and the axis of the cutter shaft 10 is changed. However, since no scale is provided to assist in the fine adjustment, it takes several times to adjust the radius R to the desired amount. Thus, the fine adjustment is time-consumingand inconvenient.
FIG. 21 of the drawings illustrates an improved boring cutter 20 that uses a screw rod 21 to adjust position of a nut seat 22 to thereby control the magnitude of the radius R (the distance from a tip of a blade 24 provided on a distal end of a cutter arm to the axis of the cutter arm 23). Bore diameter change can thus be completed easily. Nevertheless, the boring cutter 20 is expensive and complicated. If it is required to form a number of bores in a workpiece, a corresponding number of boring cutters are required. In addition, the fine adjustment is achieved by means of providing relative movements between the screw rod 21 and the nut seat 22, yet a clearance exists between the screw rod 21 and the nut seat 22. As a result, the screw rod 21 must be rotated in a reverse direction by a suitable distance before it is rotated in an opposite forwarding direction for eliminating the clearance effect, thereby assuring accuracy in the fine adjustment.
The present invention is intended to provide a fine adjusting mechanism that is simple in structure and that is easy to operate.